Paddle Wheel Research Articles

Effect of continuous and daytime mixing on Nannochloropsis growth in raceway ponds

Turbulence mixing is critical for generating high microalgal biomass productivity. Mixing also represents a major operational cost in large-scale microalgal production. The integration of photovoltaic cells with microalgae cultivation systems has been shown to eliminate the requirement of conventional grid-supplied electricity in rural areas. However, through such systems, the availability of electricity and the operation of equipment would solely depend on available sunlight and limited to only daytime. In accordance, in this study, we evaluated the effect of continuous paddle wheel mixing (24 h) and daytime mixing (12 h) on the growth, productivity and photosynthesis of Nannochloropsis sp. grown in outdoor paddle wheel driven raceway ponds operated at different depths (15 and 25 cm). Specific growth rates, volumetric and aerial biomass productivities were found to be significantly higher in ponds with 24 hour mixing compared to ponds with only 12 hour mixing operated at the same depth. The depth of the cultures did not affect the growth rate and volumetric productivity of cultures in both mixing conditions. Photosynthetic performance of cultures evaluated through chlorophyll a fluorescence measurements of photosystem II trended higher in ponds with 24 hour mixing compared to ponds subjected to 12 hour mixing. Our results clearly indicate the importance of continuous mixing to achieve high biomass productivity in cultures of Nannochloropsis sp.

How do microalgae perceive light in a high-rate pond? Towards more realistic Lagrangian experiments.

Hydrodynamics in a high-rate production reactor for microalgae cultivation affects the light history perceived by cells. The interplay between cell movement and medium turbidity leads to a complex light pattern, whose forcing effects on photosynthesis and photoacclimation dynamics are non-trivial. Hydrodynamics of high density algal ponds mixed by a paddle wheel has been studied recently, although the focus has never been on describing its impact on photosynthetic growth efficiency. In this multidisciplinary downscaling study, we first reconstructed single cell trajectories in an open raceway using an original hydrodynamical model offering a powerful discretization of the Navier–Stokes equations tailored to systems with free surfaces. The trajectory of a particular cell was selected and the associated high-frequency light pattern was computed. This light pattern was then experimentally reproduced in an Arduino-driven computer controlled cultivation system with a low density Dunaliella salina culture. The effect on growth and pigment content was recorded for various frequencies of the light pattern, by setting different paddle wheel velocities. Results show that the frequency of this realistic signal plays a decisive role in the dynamics of photosynthesis, thus revealing an unexpected photosynthetic response compared to that recorded under the on/off signals usually used in the literature. Indeed, the light received by a single cell contains signals from low to high frequencies that nonlinearly interact with the photosynthesis process and differentially stimulate the various time scales associated with photoacclimation and energy dissipation. This study highlights the need for experiments with more realistic light stimuli to better understand microalgal growth at high cell densities. An experimental protocol is also proposed, with simple, yet more realistic, step functions for light fluctuations.

The development of furrower model blade to paddlewheel aerator for improving aeration efficiency

The successful of intensive aquaculture is strongly influenced by the ability of the farmers to overcome the deterioration of water quality. The problem is low dissolved oxygen through aeration process. The aerator device which widely used in pond farming is paddle wheel aerator because it is the best aerator in aeration mechanism and usable driven power. However, this aerator still has a low performance of aeration, so that the cost of aerator operational for aquaculture is still high. Up to now, the effort to improve the performance of aeration was made by two-dimensional blade design. Obviously, it does not provide the optimum result due to the power requirements for aeration is directly proportional to the increase of aeration rate. The aim of this research is to develop three-dimensional model furrowed blades. Design of Furrower model blades was 1.6 cm diameter hole, 45º of vertical angle blade position and 30º of the horizontal position. The optimum performance furrowed model blades operated on the submerged blade 9 cm with 567.54 Watt of electrical power consumption and 4.322 m3 of splash coverage volume. The standard efficiency aeration is 2.72 kg O2 kWh-1. The furrowed model blades can improve the aeration efficiency of paddlewheel aerator.

Life cycle assessment of microalgae production in a raceway pond with alternative culture media

Microalgae production is responsible for phycoremediation and the development of green products synthesis and for cleaning processes. Studies on the environmental impacts of this process are fundamental to make these systems feasible. In these studies, a life cycle assessment of the production of microalgae biomass is important. We performed this study considering the production in wastewater or NPK medium and different methods of biomass separation. The LCA model was developed for the production of 9 and 12 kg of Desmodesmus subspicatus microalgae biomass in 10 days, which represents the production in 8000 L of wastewater and NPK solution, respectively. The total volume corresponded to 4 tanks of 2000 L each. The growth system used was an open raceway pond with culture movement caused by an air-lift system or by paddle wheels. Flocculation with NaOH and electroflotation with Al and Fe were chosen as the methods of biomass separation. These methods were chosen because they facilitate the separation using filtration or centrifugation. The final step was drying, which can be conducted with the biomass after filtration (80% water) or centrifugation (40% water). Several scenarios were examined to identify a more environmentally friendly method for microalgae biomass production. There were no differences using air lift or paddle wheels, however it was identified impacts in all stages. Also, there were fewer impacts using wastewater than using NPK. Regarding the separation of the biomass, electroflotation caused fewer impacts when compared to flocculation with NaOH. Overall, the scenario with fewest impacts was the one configured using wastewater for microalgae cultivation, followed by centrifugation and drying.

Two-Phase Flow Modeling of Solid Dissolution in Liquid for Nutrient Mixing Improvement in Algal Raceway Ponds

Achieving optimal nutrient concentrations is essential to increasing the biomass productivity of algal raceway ponds. Nutrient mixing or distribution in raceway ponds is significantly affected by hydrodynamic and geometric properties. The nutrient mixing in algal raceway ponds under the influence of hydrodynamic and geometric properties of ponds is yet to be explored. Such a study is required to ensure optimal nutrient concentrations in algal raceway ponds. A novel computational fluid dynamics (CFD) model based on the Euler–Euler numerical scheme was developed to investigate nutrient mixing in raceway ponds under the effects of hydrodynamic and geometric properties. Nutrient mixing was investigated by estimating the dissolution of nutrients in raceway pond water. Experimental and CFD results were compared and verified using solid–liquid mass transfer coefficient and nutrient concentrations. Solid–liquid mass transfer coefficient, solid holdup, and nutrient concentrations in algal pond were estimated with the effects of pond aspect ratios, water depths, paddle wheel speeds, and particle sizes of nutrients. From the results, it was found that the proposed CFD model effectively simulated nutrient mixing in raceway ponds. Nutrient mixing increased in narrow and shallow raceway ponds due to effective solid–liquid mass transfer. High paddle wheel speeds increased the dissolution rate of nutrients in raceway ponds.

A mesoporous metal-organic framework: Potential advances in selective dye adsorption

A new metal-organic framework based on manganous (II) ions and a paddle wheel ligand, H3[Mn3O3(BTB)] (Mn-BTB, HBTB = 1,3,5-tris(4-carboxyphenyl)benzene acid), was synthesized and structurally characterized. Mn-BTB was formed via self-assembly of one-dimensional (1D) helical chains interconnected through the carboxyl groups of the tripodal ligand HBTB to generate a 3D, extended network with a nanotube-like architecture and aperture size of 18.22 Å × 16.40 Å. The 2-fold self-interpenetration significantly enhanced the stability of the framework, although it minimized the empty space to some extent. Mn-BTB contains an accessible volume of 3143.6 Å3 with a 47.1% porosity, which allowed the adsorption of large dye molecules. Cationic dyes (methylene blue (MB) and rhodamine B (RhB)) and an anionic dye (methyl orange (MO)) were examined for selective dye adsorption on Mn-BTB. Mn-BTB with an anionic skeleton was beneficial for the selective adsorption of cationic dyes.

Outdoor Cultivation of Spirulina platensis for Mass Production

In the present study, the blue-green alga Spirulina platensis (NRC) was used for mass production under outdoor cultivation in three open ponds with a final capacity of 75 m3 net cultivation volume. Subculturing was performed within sequences and gradual volumes till 1,200 L open plate photobioreactor. The first and second ponds (30 cm depth) were used for the actual continuous production, while the third pond (80 cm depth) was used as a continuous inoculum supplier. In spite of low turbulence of the third pond due to high depth, all ponds had the same mechanical specification concerning paddle wheel structure and turbulence rate (16 rpm). A final nutrient concentration was employed based on Zarrouk medium by commercial grade compounds with some modifications. The nutrition was performed for the third pond by extra supplementation of extra doses of macro and micro-nutrients during the production period and dilution took place when culture was transferred to production ponds (first and second). Each production pond was harvested every 48 hours and the remainder water was return again into the third pond. The harvested pond yielded about 40 kg per day of fresh algal weight containing about 85% moisture on a dry weight basis. The results proved that using urea as nitrogen and carbon source with corn steam liquor instead of sodium nitrate and low bicarbonate, reduces production cost and supports growth medium by an adequate amount of carbon dioxide on the expense of the luxury use of sodium bicarbonate (16.8 g.l-1). Chemical analysis of the produced biomass showed 58-62% crude protein, 6-8% of ether extract and 8-11% of total carbohydrates. S. platensis contained total essential amino acids (131.3 mg/g), with a predominance of arginine followed by glutamic acid, leucine and phenylalanine.

In line monitoring of the powder flow behavior and drug content in a Fette 3090 feed frame at different operating conditions using Near Infrared spectroscopy

Near infrared (NIR) spectroscopy was used to determine the drug concentration in 3% (w/w) acetaminophen blends within the complex flow regime of the tablet press feed frame just before tablet compaction. NIR spectra also provided valuable information on the powder flow behavior within the feed frame and were used to track when a process enters or leaves the steady state. A partial least squares regression calibration model was developed with powder mixtures that varied from 1.5 to 4.5% (w/w) by obtaining 135 spectra after steady state for each concentration while the feed frame and die disc operated at 30.5 revolutions per minute (rpm). The calibration model determined drug concentration in validation blends with a root mean square error of prediction and bias below 0.1% (w/w). The robustness of the NIR calibration model was evaluated by determining the effect of variation on the operating conditions (paddle wheel speed and die disc speed) on NIR predictions. This work found that the paddle wheel speed can be increased up to 30% and the die disc speed decrease 10% without affecting NIR predictions. The results demonstrated that paddle wheel speed has a significant effect on the wave powder behavior (frequency and amplitude) but does not have significant effect on the mass hold-up within feed frame. The die disc speed does not affect wave powder behavior but affects significantly the mass hold-up inside the feed frame. This information can be used to reduce the tablet weight variability and ensure that this critical attribute is met.

Exploiting Dimensional Variability in Cu Paddle-Wheel Secondary Building Unit Based Mixed Valence Cu(II)/Cu(I) Frameworks from a Bispyrazole Ligand by Solvent/pH Variation

Four coordination polymers, [CuII(L)H2O]·2DMF (1), [CuICuII2L2(H2O)(pyridine)2]·(NO3)·4DMF·3H2O (2), [CuICuII2L2(pyridine)3]·(NO3)·DMF·4H2O (3), and [CuII2L(μ-O)(DMF)]·4DMF·5H2O (4), have been synthesized under solvothermal conditions using a single methylene-bispyrazole based carboxylic acid ligand, L, and Cu(NO3)2. All the compounds were comprised of copper paddle wheel secondary building units (SBUs). The structural differences in 1–4 arise due to different compositions of the solvent system as well as pH of the medium. Compound 1 exhibited a one-dimensional (1D) double chain structure with a porous three-dimensional (3D) supramolecular network, while 2 and 3 represent mixed Cu(II)/Cu(I) based porous frameworks. MOFs 2 and 3 were obtained by systematic binding of pyridine molecules on the axial positions of Cu paddle-wheel SBU, having a rare topology, sur; bbf-3,4-Cccm and a new topology, respectively. MOF 4 is a 3D porous network containing a Cu2(μ-O)2 moiety and exhibits a 3,4,4-c net. It contains op...

Study of Flow Characteristics of Air in DI Diesel Engine by Modification in Intake Valve

This project work involves experimental investigation of intake valve to generate swirling of air fuel mixture inside cylinder for Direct Injection (D.I) diesel engine. Three different types of intake valves having different configuration on its face are studied. The average swirl number and flow coefficient is obtained using a paddle wheel test bench. Swirl ratio is the ratio of rotary speed of the paddle wheel in a swirl measurement test rig, to the engine speed as calculated by measuring flow rate of intake air. The second part of work focused on the Computation Fluid Dynamics (CFD) to study flow distribution and flow velocity inside cylinder. The simulations are carried out on different valve lifts ranging from 4mm to 13mm on Ansys 16. Intake valves with four blades on valve seat shows better results for swirl ratio and flow coefficient in one of the cases when compared to base geometry. With this modification in intake valve results of this work shows improvement in swirl generation and flow distribution.

Cyclophosphazene-Based Hybrid Nanoporous Materials as Superior Metal-Free Adsorbents for Gas Sorption Applications.

Cyclophosphazene-based inorganic-organic hybrid nanoporous materials (CHNMs) have been synthesized by a facile solvothermal method. The condensation of pyrrole with the reaction product of phosphonitrilic chloride trimer and 4-hydroxybenzaldehyde resulted in the formation of high-surface-area CHNMs. The maximum specific surface area (SABET) of 1328 m2 g-1 with hierarchical pore structures having micropores centered at 1.18 nm and mesopores in the range of 2.6-3.6 nm was estimated from the N2 sorption analysis. Observation of high SABET could be attributed to the synergy effect exerted by the cyclophosphazene moiety owing to its three-dimensional paddle wheel structure. The metal-free adsorbent exhibited a high and reversible CO2 uptake of 22.8 wt % at 273 K and 1 bar. The performance is on the higher side among the reported metal-free inorganic-organic hybrid nanoporous adsorbents. Moreover, the high H2 uptake of 2.02 wt % at 77 K and 1 bar is an added advantage. The superior performance of the adsorbents for the gas sorption applications could be attributed to the combined effect of high SABET and hierarchical pore structure, which has made CHNMs good candidates for energy and environmental applications.

Determination of the Structural Characteristics of Microalgal Cells Walls under the Influence of Turbulent Mixing Energy in Open Raceway Ponds

Turbulent flow mixing is essential in optimizing microalgal cultivation in raceway ponds. Microalgal cells are however highly sensitive to hydrodynamic stresses produced by turbulent mixing because of their small size. The mechanical properties (wall deformation and von Misses stress) of the microalgal cell wall structure under the influence of turbulent mixing are yet to be explored. High turbulence magnitudes damage microalgal cell walls by adversely affecting their mechanical properties which consequently destroy the microalgal cells and reduce the biofuel production. Therefore, such a study is required to improve the biofuel productivity of microalgal cells before their cell wall damage in raceway pond. This study developed a novel fluid–structure interaction (FSI)-based numerical model to investigate the effects of turbulent mixing on the cell wall damage of microalgal cells in raceway ponds. The study investigated microalgal cell wall damage at four different locations in a raceway pond in consideration of the effects of pond’s hydrodynamic and geometric properties. An experiment was conducted with a laboratory-scale raceway pond to compare and validate the numerical results by using time-dependent water velocities. Microalgal cell wall shear stress, cell wall deformation, and von Misses stress in the raceway pond were investigated by considering the effects of aspect ratios, water depths, and paddle wheel rotational speeds. Results showed that the proposed numerical model can be used as a prerequisite method for the selection of appropriate turbulent mixing. Microalgal cell wall damage is high in shallow and narrow raceway ponds with high paddle rotational speeds.

Development and validation of an in-line NIR spectroscopic method for continuous blend potency determination in the feed frame of a tablet press

A calibration model for in-line API quantification based on near infrared (NIR) spectra collection during tableting in the tablet press feed frame was developed and validated. First, the measurement set-up was optimised and the effect of filling degree of the feed frame on the NIR spectra was investigated. Secondly, a predictive API quantification model was developed and validated by calculating the accuracy profile based on the analysis results of validation experiments. Furthermore, based on the data of the accuracy profile, the measurement uncertainty was determined. Finally, the robustness of the API quantification model was evaluated.An NIR probe (SentroPAT FO) was implemented into the feed frame of a rotary tablet press (Modul™ P) to monitor physical mixtures of a model API (sodium saccharine) and excipients with two different API target concentrations: 5 and 20% (w/w). Cutting notches into the paddle wheel fingers did avoid disturbances of the NIR signal caused by the rotating paddle wheel fingers and hence allowed better and more complete feed frame monitoring. The effect of the design of the notched paddle wheel fingers was also investigated and elucidated that straight paddle wheel fingers did cause less variation in NIR signal compared to curved paddle wheel fingers. The filling degree of the feed frame was reflected in the raw NIR spectra. Several different calibration models for the prediction of the API content were developed, based on the use of single spectra or averaged spectra, and using partial least squares (PLS) regression or ratio models. These predictive models were then evaluated and validated by processing physical mixtures with different API concentrations not used in the calibration models (validation set). The β-expectation tolerance intervals were calculated for each model and for each of the validated API concentration levels (β was set at 95%). PLS models showed the best predictive performance. For each examined saccharine concentration range (i.e., between 4.5 and 6.5% and between 15 and 25%), at least 95% of future measurements will not deviate more than 15% from the true value.

Phycoremediation: An Eco-Solution to Environmental Protection and Sustainable Remediation

Phycoremediation involves the remediation of contaminants in a water body using algae (micro and macro). Algae fix carbon-dioxide by photosynthesis and remove excess nutrients effectively at minimal cost. It removes pathogens and toxic materials from waste water. Xenobiotics, chemicals and heavy metals are known to be detoxified, transform, accumulated or volatilized by algal metabolism. It offers advantage over conventional methods of remediation by its effectiveness, efficiency and eco-friendly nature. Commercially, it involves design and construction of Waste Stabilization Pond System (WSPs) and High Rate Algal Ponds (HRAP) with difference in that WSPs are unmixed or involves a little mixing, so can experience stratification, but the HRAPs involves process of mixing using paddle wheel. There are industries that are commercially involved in phycoremediation and they experience cost reduction and maximization of profit compared to the convectional system of remediation.

Bimetallic metal organic frameworks with precisely positioned metal centers for efficient H2 storage.

We demonstrated that the ratio and position of two different metal ions, Pd and Cu, can be precisely controlled within MOFs through predesigned metal clusters. These MOF structures incorporating Pd-Cu paddle wheel units were synthesised simply by reacting Pd-Cu acetate metal clusters and tritopic organic linkers at room temperature. Pd-Cu open metal sites were found to be uniformly distributed throughout the MOFs with a ca. 1 : 1 ratio. The incorporation of Pd into the MOF structure also led to enhanced affinity towards H2 with Qst values up to 8.9 kJ mol-1.

Theoretical Investigations of the Spin Hamiltonian Parameters for the Mononuclear Square Pyramidal [CuO5] Groups in Two Paddle Wheel Copper Complexes

The spin Hamiltonian parameters (SHPs) (g factors and hyperfine structure constants) for the mononuclear square pyramidal [CuO5] groups in two paddle wheel copper complexes {Cu2(μ2–O2CCH3)4}(OCNH2CH3) and \({}_{\infty }^{3} [{\text{Cu}}_{ 2}^{\text{I}} {\text{Cu}}_{ 2}^{\text{II}} ( {\text{H}}_{ 2} {\text{O)}}_{ 2} {\text{L}}_{ 2} {\text{Cl}}_{ 2} ]\) are theoretically investigated from the perturbation calculations of these parameters for a rhombically elongated octahedral 3d 9 group. The slightly larger anisotropy Δg (≈ g // − g⊥) of complex 1 than complex 2 is attributed to the slightly bigger deviations of the polar angles related to the ideal value 90° and relative differences between the axial and basal Cu–O distances in the former. The axiality of the EPR signals for both systems can be illustrated as the fact that the perpendicular anisotropic contributions to X and Y components of the SHPs arising from the four basal ligands with slightly distinct bond lengths and bond angles may roughly cancel one another. The signs of hyperfine structure constants are also theoretically determined for both complexes.

Combined Experimental and Computational Study on Catalytic Cyclocoupling of Epoxides and CO2 Using Porphyrin-Based Cu(II) Metal-Organic Frameworks with 2D Coordination Networks

Abstract The cyclocoupling of epoxides and CO2 was investigated using porphyrin-based Cu(II) metal-organic frameworks with 2D coordination networks. A variety of mono- and disubstituted epoxides were transformed into cyclic carbonates under mild and neat conditions. Several control experiments were carried out to elucidate that the catalytically active site is the dicopper paddle wheel unit rather than the copper porphyrin complex moiety. The proposed mechanism was corroborated by density functional theory calculations of a model paddle wheel unit.

A porous zinc(II) metal–organic framework exhibiting high sensing ability for ferric and nitroaromatics as well as photocatalytic degradation activities against organic dyes

A NbO-type Zn(II) metal–organic framework of {[Zn2(HL)(H2O)2]∙H2O}n (1) has been developed using a pentacarboxylate 2,5-bis(3′,5′-dicarboxylphenyl)-benzoic acid (H5L) ligand and characterized. The single-crystal X-ray diffraction studies indicate that 1 comprises free –COOH groups and Zn(II) centers bridged by four carboxylate groups to form a paddle wheel SBU which is further connected by L5− ligands to build a 3-D porous network with two types of cages. The chemically stable MOF 1 behaves as a highly selective and sensitive fluorescent chemosensor for the detection of Fe3+ ions, 2,4,6-trinitrophenol (TNP), which is known to be an extremely hazardous and strong explosive. Furthermore, the photocatalytic properties of 1 for degradation of methyl violet (MV) and Rhodamine B (RhB) have been explored. The possible emission quenching mechanism in the presence of nitro-aromatics (NACs) has been addressed by theoretical calculations and photocatalytic activity of 1 against organic dyes has been supported using density of states (DOS) calculations.

УПРАВЛЕНИЕ СУДНОМ С КОЛЕСНЫМ ДВИЖИТЕЛЬНО-РУЛЕВЫМ КОМПЛЕКСОМ ПРИ ВЫПОЛНЕНИИ ШВАРТОВЫХ ОПЕРАЦИЙ

In Russia radically new ships with wheeled propulsion-steering complex have appeared. They do not have a traditional steering wheel. Steering is exercises by changing the ratio of the paddle wheels rotation frequency. That provides improved maneuverability of the vessel, but at the same time creates significant difficulties for the navigator while holding the vessel on a predetermined course and mooring operations. The article suggests equipping the ship with an azimuth bow thruster in order to improve its operational characteristics. The article presents dynamic characteristics of the ship while using thrusters. Simulating results show that using a thruster on board the ships with wheel-propulsion and steering complex greatly improves maneuverability at low speeds, but is considered inexpedient at higher speeds.

PERFORMANCE EVALUATION OF A DEVELOPED PADDLE AERATOR ON CATFISH EFFLUENTS IN LAGOS STATE, NIGERIA

Catfish production is one of the largest segments of fish culture in Lagos State, Nigeria. However, catfish effluents, which usually deteriorate the environment, need to be controlled. The effect of paddle-wheel aerator in catfish effluent was evaluated. The volume of catfish effluent was collected into two basins and diluted at given ratios. The paddle-wheel aerator was installed in one basin, while another basin served as control in determining the impact of paddle wheel aerator on catfish effluents. Water qualities such as Total Suspended Solids (TSS), Total Nitrogen (TN), Total Phosphorus (TP), Total Ammonia (TNH3) and Nitrite (NO2-N) and Biochemical oxygen demand (BOD5) examined and ana-lysed. Results indicated that paddle-wheel aerator reduced TSS (24.4±1.5 %), TN2-N (53.3±1.2 %) , TNH3-N (65.2±1.2 %) , NO2-N (97.1±1.1 %) , TP (61.8±1.1 %) and BOD5 (54 ±1.5 %). com-pared with natural purification 33.9±1.6 % of TSS, 22.7±1.4 % of TN2-N, 29.3±1.6 % of TNH3-N, 53.9±1.2 % of NO2-N, 21.6±1.5 % of TP and 15.4±1.6 % of BOD5 at the same dilution ratio There were significant different (P ≤0.05) between paddle wheel aerator and natural purification in concen-trations reduction. The paddle wheel aerator was found to be relevant in the water quality improve-ment and thus recommend for small and medium scale fish farmers in controlling effluents.